Polymerizations initiated by saturated cyclic terpene peroxides



United States Patent 2,775,578 POLYMERIZATIONS INITIATED BY SATURATED CYCLIC TERPENE PEROXIDES Gordon S. Fisher, Lake City, Plan, and Leo A. Goldblatt,

,New Orleans, La., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Application March 22, 1955, Serial No. 496,085

13 Claims. (Cl. 260-841) (Granted under Title 35, U. s. Code (1952 sec. 266) oxide. This application is a continuation-in-part of our copending application, Serial No. 199,910, filed December 8, 1950, now Patent No. 2,735,870.

Since the discovery that rubber-like polymers of improvided quality are produced by polymerizations conducted at temperatures below normal room temperature,

numerous polymerization formulations and procedures have been developed for use in low temperature aqueous emulsion polymerization processes. In general, while the employment of the low temperature reaction improves the polymer quality, in many cases it is attended by dis advantages, such as a lowered reproducibility, lowered rate of reaction, increased induction time, and the like.

A primary objectof the present invention is to provide an improved process for the polymerization of unsaturated organic compounds, which process is particularly applicable to the low temperature process of producing synthetic rubber. A further object is to provide an improved method of causing unsaturated organic compounds to polymerize in a reproducible manner and at a relatively I rapid rate at a relatively low temperature in an aqueous emulsion. Other objects and advantages of the invention will be apparent from the tollowing description and claims.

We have now discovered that a process of polymerizing unsaturated organic compounds in the presence of an organic peroxide, particularly when the polymerization is conducted in an aqueous emulsion red-ox formulation containing the peroxide as an oxidizing agent, is materially improved, particularly in therrate and reproducibility of the polymerization reaction, when the peroxide used is a saturated cyclic terpene peroxide.

In general, in accordance with this invention, polymerizable unsaturated organic compounds are polymerized by mixingthem with saturated cyclic terpene peroxides and decomposing the peroxides to form free radicals.

Our copending application, Serial No. 199,910, filed December 8, 1950, Patent No. 2,735,870, describes and claims saturated cyclic terpene peroxides and processes for their production. of saturated cyclic terpene hydrocarbons produced in accordance with the process of our oopendingapplication comprise saturated cyclic terpene peroxides suitable for employment in the process of the present invention. The

oxid'ates are solutions in whichthe solvent consists essentially of saturated cyclic terpene hydrocarbons, and the Both the peroxides and oxidates 2 solute consists essentially of the predominant hydroperoxy products produced in situ by oxidizing the solvent saturated cyclic terpene hydrocarbons, in liquid phase, with gaseous oxygen, until the solvent contains at least about 20% by weight of saturated cyclic terpene peroxides.

As usedherein, the term peroxides is generic and includes *hydroperoxides, The term saturated cyclic terpenes refers to compounds which, structurally, are obtainable from cyclic terpenes by the saturation, of. their double bonds and to mixtures of such compounds with inert substances, with-out regard to the particular method of starting material used to produce the mixture. Saturated cyclic terpene radical names produced by replacing e with y e. g. pinanyl from pinane, refer to monovalent radicals formed by the removal of anyhydrogen atom from the hydrocarbon.

i The peroxides produced by the process of our copending application are principally hydroperoxides. When they, are produced from saturated monocyclic terpenes, they have the empirical formula C10H19OOH, and when they are produced from saturated bicyclic terpenes they have the formula CmHnOOH. The following schematic formulas are illustrative of the structures of particularly valuable monoand bicyclic saturated terpene hydroperoxides:

I OOH H The saturated cyclic terpene hydrocarbon oxides can be concentrated by any of the conventional methods. For example, a low pressure carrier gas distillation to strip off the unoxidized hydrocarbon leaving the peroxide as a residue, a low pressure vacuum distillation of the peroxide, or a precipitation of the hydroperoxide as the sodiumsalt, are satisfactory methods for the isolation of the saturated cyclic terpene hydroperoxides.

The oxidates are excellent starting materials for the preparation of substantially pure saturated cyclic terpene hydroperoxides. Simple removal of the unoxidized hydrocarbon by suitable distillation, such as a low pressure steam distillation, usually leaves substantially pure hydroperoxides as the residue. Since some non-volatile oxygenated by-products may be produced, particularly in the latter stages of oxidation, oxidates containing only about 30 to 60% hydroperoxides are generally preferred for the preparation of the substantially pure hydroperoxides by distillation methods. Other methods of concentration, such as precipitation of the hydroperoxide as the sodium salt or extraction of the hydroperoxide from the oxidate with aqueous or alcoholic base and subsequent regeneration of the hydroperoxide from the salt, may also be applied to oxidates prepared by our process.

Monomers suitable for polymerization in accordance with theprocess of this invention comprise polymerizable unsaturated organic compounds capable of being dispersed in an aqueous emulsion. In general, such unsaturated organic compounds contain not more than about 10 carbon atoms and are characterized by the presence of at least one CH2=C group attached to electronegative groups such as halogen atoms, or vinyl, acetylenic, phenyl, nitrile, carboxy, or the like groups. Illustrative examples of suitable unsaturated compounds include conjugated butadienes such as butadiene, 3-methoxy-l,3- butadiene, and the like; haloprenes such as chloroprene, bromoprene, and the like; alkenyl aromatic hydrocarbons such as styrene, vinyl, naphthalene, and the like, acrylic and substituted acrylic esters and their nitriles, amides,

and the like, such as acrylic acid, methyl methacrylate,

acrylonitrile, methacrylamide, and the like; methyl vinyl ketone, vinyl acetate, and the like; and mixtures thereof. M xtures of polymerizable aliphatic conjugated diolefins, such as butadiene, with copolymerizable vinylaromatic hydrocarbons, such as styrene, 'are preferred'starting materials;..especiall y when the mixtures contain about 1 to l parts by weight diolefin per part byweightof aromatic hydrocarbon.

Polymerizations conducted in accordancewith the present invention can be conducted in bulk or in solutions, dispersion's,- or suspensions in the usual organic or'aqueous liquid solvents or reaction medium. Illustrative examples of suitable liquids include hydrocarbons such as the pentanes, hexanes, benzene and the like; substituted hydrocarbons -such as nitrobenzene, chlorobenzene and the like; and aqueous solutions, dispersions and emulsions having a pH of from about 6 to 12.

The polymerization reactions can be conducted under normal or. superatmospheric pressure; and are preferably conducted in a neutral atmosphere such as a nitrogen atmosphere. The reactions can be conducted at temperatures ranging from relatively low temperatures which are slightly above the freezing point of the reaction mixture, particularly Where a redox formulation is used, to relatively high temperatures which are slightly below the decomposition temperature of the monomers or polymers, or temperatures at which the rate of decomposition of the peroxides becomes unduly rapid. In general, temperatures ranging from about l0 to 130 C. can be used, and where aqueous emulsion redox formulations are used, temperatures ranging from about 0' to 10 C. are preferred.

The process of this invention is particularly adapted for the copolymerization of monomers comprising mixtures of aliphatic diolefins and vinyl aromatic hydrocarbons in an aqueous emulsion redox formulation comprising water, a reducing agent or activator, an emulsifying agent, a modifier, and the organic peroxide.

In general, the reducing agent or activator can comprise any of the usual activators consisting of one or more compounds which produce astandard oxidation potential of below about minus 0.3 volt. Illustrative examples of suitable activators include the polyamino compounds such as hydrazine, ethylenediamine, tetraethylenepentamine and mixtures of such polyamino compounds with other activator compounds; soluble compounds containing ion-s of metals such as iron, cobalt, manganese, copper, vanadium, and the like present in both a high and low valence state, such as aqueous mixtures containing FESOi, and Na4P2O7 or the sodium or potassium complex salts thereof, and mixtures of such compounds with other activator compounds; and mixtures of metal ion containing compounds with reducing sugars such as dextrose, threose, glucose, and the like. Activators of the low sugar or sugar-free type containing ferric and ferrous ions are preferred.

The amount of the activator can be varied widely depending upon the particular activator and the other components of the polymerizing mixture; but, in general, from about 0.1 to 5 parts per hundred parts of monomer can be used.

The emulsifying agent can comprise substantially any of the emulsifying agent-s usually used in aqueous emulsion polymerizations. Illustrative examples of suitable emulsifying agents include the alkali metal salts of the higher fatty acids, or the rosin acids, and the like, or the non-ionic emulsifying agents, such as the alkyl or aromatic sulfonates, and the like. The alkali metal salts of the rosin acids and the chemically modified rosin acids are preferred.

The amount of the emulsifying agent can be varied from about 0.5 to 15% based on the total weight of the aqueous emulsion; but the use of from about 1 to 3% is preferred.

ondary, or tertiary mercaptans usually used to modify polymerization reactions. captans is preferred.

The amount of the modifier can be varied from about 0.1 to 1.0% based on the weight of the monomers; but the use of from about 0.2 to 0.5% is preferred.

In conducting the polymerization, the components of the polymerization reaction, consisting essentially of water, an activator, an emulsifying agent, the monomers, a reaction modifier, and the saturated cyclic terpene peroxide can be mixed in substantially any order. It is generally preferable, particularly in a batchwise or semibatchwise process, to first charge the reaction vessel with an aqueous medium into which the activator has been incorporated, then add the monomers, so that the peroxide, which' can be added along with the monomers, is the last reactant introduced into the reaction vessel.

The various additives and modifying susbtances usually employed in emulsion polymerization reactions can be employed in polymerizations conducted in accordance with the present invention using the amounts usually used, for the usual purposes. Where it is desirable to polymerize at temperatures below 0 C., water soluble substances, such as inorganic salts and alcohols, glycols and the like can be used to lower the freezing point of the aqueous medium. Suitable water soluble substances include methyl or ethyl alcohol, ethylene, glycol, and the like.

The followin'gexamples are illustrative of the invention.

Variations in emulsifiers, modifiers, and activators used in ,emulsion copolymerizat-ions may alter the rate of conversion obtained with a given perioxide. The saturated cyclic terpene peroxides were compared with other peroxides by holding all other variables constant and running the polymerizations at the same time in identical reactors.

The formulations used in the examples below are standard recipes for production of the so-called cold rubber at 5 C. using cumene hydroperoxide' (CHP) and di-isopropyl benzene monohydroperoxide (DIBP) as the peroxides. As Will be apparent to those skilled in the art, these formulations are not necessarily the optimum, and many variations in the recipes or formulations as well as the polymerization temperature may be made without departing from the spirit and scope of our invention.

The general recipe used in the following examples of emulsion polymerizations was:

The use of the tertiary mer- Ingredient: Parts -Butadiene 71.5 Styrene 28.5 Mercaptan modifier 0.2

Rosin type soap 4.7

Water Activator Varied Peroxide Varied Example 1 In order to demonstrate the variation of the activity of hydroperoxides as polymerization catalysts with the variation in the number of double bonds in the hydroperoxide molecule, peroxides derived from terpenes and containing 3, 2, 1 and no double bonds wete used as the catalyst in the above formula using a Standard low-sugar iron activator (Fe SO47H2O, 0.12 part, W-rPzOr, 1.107 parts and Cerelase 1.0 part, per'100 parts of monomers).

Example 5 Concentrates of pinane hydnoperoxide (PEP-40%) and (PHP87%) prepared by the method of our copending application, were used, in comparison with a 1 5 was ga 5 ti e-ye fg l for fg 5 commercial sample of di-isopnopyl benzene monohydron a cises m m 0 perqxl was use r peroxide (DIBP50.%) as the catalyst in the above grams 0 monomers formulation, using an amine activator tetraethyleneof monomel's 9; Polymer as determmed pen-tamine, 0.20 part per 100 parts of monomer). The after 10 hours was peroxide concentrates were employed in amounts provid- 1O ing about 0.15 part of peroxide per 100 parts of monomer. Peroxide oi- Double Conversion bonds Percent,

10 hours Conversion, percent Peroxide iiigiig giijjjii"' """"II:III"'I g is? 8 hours 1211mm beta-pinene 1 3 p-menthane. 0 54 PEP-50% 53 67 DIBP 8 47 PEP-87%.... 60 71 DIBP-50% 59 64 Example 2 v 0 A concentrate of p-menthane hydroperoxide (MHP) 8 Example 6 containing 59 percent of MHP by weight prepared by the Samples of styrene containing 1% by weight of the method of our copending application was used as the indicated peroxides were thermally polymerized by heatcatalyst in the low-sugar iron activated formula described ing them at 100 C. for the indicated times. The effiin Example 1 using 0.05 part by weight of peroxide per ciency of the peroxides were compared on the basis of how 100 parts of monomers. A commercial sample of CHP much the physical properties of the so-heated mixtures containing 68 percent by weight of the peroxide and a differed from those of the initial mixture of pinane,hydrocommercial sample of DIBP containing 50 percent by peroxide, and styrene (referred to as I). weight of the peroxide were used as the catalyst in the same formula at the same peroxide concentration for Appearance after heating at 100 0. for comparative purposes. Conversions determined at 4 mater hour intervals were: 60 min. 100 min. 200 min.

Conversion, percent Pinane hydroperdxide. More viscous Very inuch Hard, clear, Peroxide 3 than (I) more vissolid.

9 cous than 4 hours 8 hours I Tertiary butyl hydro- Less viscous More vis- Rubberymass.

peroxide. oous than cous than 66 81 31 41 49 49 We claim: Example 3 1. In a process of polymerizing polymerizable unsaturated organic compounds by mixing them with an organic P1113113 Y P was used "3 the catalyst peroxide and decomposing a peroxide to form free radi- 111 vgenfiral Taupe with the low'sugar f actlvator cals, improvement which comprises employing as the ordfiscflbfid 1n Exampl? DIBP was used the same ganic peroxide a saturated cy-clic tenpene peroxide. formula for comparative purposes. The amount of pure In a process of polymerizing polymerizable unsaub hydroperoxide charged in each case was 0.06 part by rated Organic compounds by mixing thgm with an op weightper 100 parts of monomers. The conversions garlic peroxide and thermally decomposing the peroxide detel'mlned at 4 hour Intervals were: to form free radicals, the improvement which comprises 50 employing as the organic peroxide a saturated cyclic ter- Conversion, Percent pene peroxide. Pemxlde 3. In a process of polymerizing polymer-izable unsatu- 8 hours 12 hours rated organic compounds by reacting them with an aqueous emulsion redox formulation containing an organic 2g g; peroxide as an oxidizing agent, the improvement which comprises employing as the organic peroxide a saturated cyclic terpene peroxide. Example 4 4. The process of claim 3 in which the polymerization is conducted at from about 0 to 10 C. Pmane hydropel'oxlde (PHP) was used i the catalyst 5. In a process of polymerizing a mixture of polymer- III the general Emmi-11a wlth a sugarjfree acuvamr izable conjugated aliphatic dio'lefins and vinyl aromatic (F SO 7I-I O, 0,12 art, and K P2O7, 0.107 part, p 100 hydrocarbons by. reacting the hydrocarbons with an aque- Parts of monomer)- As the Preceding examples DIBP ous emulsion redox formulation containing an organic was used same fopmuia for c'ompara'twe Purposes peroxide as an oxidizing agent, at a temperature of from Two concentrations of peroxides were used. The concenabout 0 to curhe improvement which comprises trations used and the conversion at 4 hour intervals were: ploying as the Organic Peroxide a saturated cyclic pene peroxide. 7 i P P t Conversion, Percent 6. The process of claim 5 in which the redox formulae at 5 tion contains a sugar-free ferric and ferrous ion contain- 4hours ShOIllS 12hours i a tivam 7. The process of claim 5 in which the redox formulagg g2 5; tion contains a low sugar ferric and ferrous ion con 15 17 17 taining activator. 29 32 33 8. The process of claim 5 in which a saturated cyclic terpene oxidate containing at least 20% saturated cyclic to form freeradicals the step of employing as the organic peroxide a saturated cyclic tenpene peroxide. 13-. The process of claim 12 in which the polymerization is conducted at a temperature of about 100 C.

References Cited in the file of this patent Fisher et a1.: Ind. and Eng. Chem., vol. 43, No. 3, March 1952, pages 671-674.

Cooper Chemical Society Journal, April 1953, pages it with an organic peroxide and decomposing the peroxide 10 1267-1271. 

1. IN A PROCESS OF POLYMERIZING POLYMERIZABLE UNSATURATED ORGANIC COMPOUNDS BY MIXING THEM WITH AN ORGANIC PEROXIDE AND DECOMPOSING A PEROXIDE TO FORM FREE RADICALS, IMPROVEMENT WHICH COMPRISES EMPOLYING AS THE ORGANIC PEROXIDE A SATURATED CYCLIC TERPENE PEROXIDE. 